KR20040009106A - Magnetohydrodynamic barrier embedded micromixer and method for fabricating thereof - Google Patents

Abstract

PURPOSE: A magnetohydrodynamic barrier embedded micro mixer and a method for manufacturing the same are provided to achieve superior chaotic mixing by periodically creating and extinguishing a hyperbolic point based on a spiral flow formed in a micro channel. CONSTITUTION: At least one barrier(161) is aligned on an upper channel plate(162) so as to achieve superior chaotic mixing, thereby forming a magnetohydrodynamic barrier embedded micro mixer(160). Metal is deposited on the surface of a first substrate through thermal deposition. Then, an electrode is formed through an ultraviolet photo process. A protective layer is formed on a surface of the first substrate. A micro channel wall is formed on the protective layer through a photo process. An aluminum film is formed on the micro channel through a sputtering process. After coating photosensitive material on a second substrate, a space for forming a barrier is formed through an ultraviolet photo process. An upper micro channel plate is formed on the second substrate.

Description

MAGNETOHYDRODYNAMIC BARRIER EMBEDDED MICROMIXER AND METHOD FOR FABRICATING THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromixer and a method for manufacturing the same, and more particularly, to spirally induced inside a microchannel by magnetohydrodynamic propulsion by controlling the direction of an electric field and a magnetic field by properly arranging electrodes on a microchannel wall. A technique for inducing chaotic mixing of fluids by introducing one or more barriers to the microchannel walls based on helical flow.

With the miniaturization of analytical technology, research and development of micro devices that can process and analyze a large number of samples and reagents in small units are being conducted.In addition, bio-chip and lab-on-a-chip And Micro-Total-Analysis-System fall into this category. Miniature devices such as biochips, lab-on-a-chip and micro-total-analysis-systems perform all the processes required for analysis on one small chip It may include several channels or microstructures. At this time, it is essential to effectively mix the sample and reagent carried by the microchannel for the analysis or (bio) chemical reaction in such a micro device. In existing large-scale systems, it is possible to induce turbulent flow with a large enough Reynolds number if the propeller is turned in the fluid or moving parts such as magnetic beads are introduced into the fluid. Thus, a mixture of fluids was obtained. However, in the case of a very small system, since the Reynolds number is greatly reduced, since turbulence is not formed in addition to the laminar flow, it is difficult to expect only mixing by diffusion, and as a result, it is difficult to obtain a uniform mixture of fluids.

Accordingly, many kinds of micro mixers have been proposed for effective mixing at the micro level, and the mixing mechanisms of these mixers are affected by how the fluid is driven. This is because the micromixer is used as an element of the overall analysis system. The actuation of the fluid in the microchannels is achieved by mechanical micropumps, such as micropumps, syringe pumps, etc., which cause flow by pressure, and non-mechanical micropumps that utilize electrohydrodynamic, electroosmosis, electromagnetic forces, and the like. . The micro-pump method using the electromagnetic force can be applied to a bio-system because the applied voltage is smaller than other methods, and by using an alternating voltage can prevent the electrolysis of the electrode exposed to the fluid as an effective driving source of the fluid It can be thought of.

The electromagnetic propulsion method using AC voltage is described by AV Lemoff and AP Lee, An AC magnetohydrodynamic micropump, Sensors and Actuators B , Vol. 63, pp. 178-185, 2000.

In addition, based on this electromagnetic propulsion method, the method of improving the mixing by rotating the fluid in the circular flow path and increasing the contact surface of the two fluids is described in JP Gleeson and J. West, Magnetohydrodynamic Micromixing, 5th international conference on Modeling and Simulation of Microsystems (MSM) , pp. 318-321, Puerto Rico, April 21-25, 2002. HH Bau, J. Zhong and M. Yi, A minute magneto hydro dynamic (MHD) describes a method of stirring the stationary fluid through an electromagnetic force. ) mixers, Sensors and Actuators B , Vol. 79, pp. 207-215, 2001. Studies have been conducted to achieve effective mixing of the fluids through these methods.

However, the method of inducing mixing by rotating the flow driven by the electromagnetic force in the circular flow path is difficult to obtain effective mixing because the mixing method is based on the linear flow, and the fluid is stopped in the method of stirring the stationary fluid through the electromagnetic force. Not only are they unsuitable for systems with continuous flow, but there is also a risk of electrolysis of the electrodes due to the DC voltage used.

Therefore, the design of the micro mixer that can expect more effective mixing performance through the structure of the simple shape along with the design of the size and direction of the electric and magnetic fields for the fluid drive based on the electromagnetic propulsion method.

In order to solve the problems of the prior art, the present invention induces the helical flow of the fluid by the electromagnetic force through the proper design of the size and the direction of the electric field and the magnetic field, and at the same time introduces a simpler microstructure of the pressure loss Micromixer and its manufacture inducing higher chaos mixing at micro size by introducing periodic disturbances in which hyperbolic points are periodically created and dissipated based on the helical flows formed in the microchannels while minimizing The purpose is to provide a method.

In order to achieve the above object, the present invention includes electrodes for forming an electric field capable of causing helical flow on the side walls and the bottom of the microchannel, and magnetic field generating means for forming a magnetic field around the outside of the microchannel. It is provided to provide an electromagnetic force-propelled micro mixer with a barrier, characterized in that one or a plurality of barriers are arranged on the micro channel wall to induce chaotic mixing.

In another aspect, the present invention comprises the steps of depositing a metal on the surface of the first substrate by thermal evaporation to form an electrode through an ultraviolet photography process; Forming a protective layer on a surface of the substrate on which the electrode is formed; Forming a microchannel wall surface inducing a spiral flow on the protective layer through an ultraviolet photographic process; Forming an aluminum thin film on the microchannel through a sputtering process; Forming an electrode on the side wall of the channel to induce longitudinal flow of the aluminum thin film through an ultraviolet photographing process; Etching the exposed protective layer inside the channel to expose a channel bottom electrode causing a cross flow to fabricate a microchannel underplate; Applying a photosensitive material on the second substrate and forming a space where a barrier is to be formed through an ultraviolet photographing process or the like; Manufacturing a microchannel upper plate by molding and curing the polydimethylsiloxane (PDMS) on the second substrate; It provides a method of manufacturing an electromagnetic force-propelling chaos micro mixer comprising a barrier including the step of adhering the micro-channel upper plate and the lower plate.

Accordingly, the present invention proposes a micro mixer capable of obtaining chaotic mixing despite the introduction of a simpler shape microstructure, while presenting a design that induces a helical flow inside the micro channel through the electromagnetic force.

1 is a view showing the flow of the fluid caused by the electromagnetic force propulsion,

2 shows a cross section of an overall system structure according to the invention,

3a and 3b are views showing the cross-sectional flow form of the helical flow and the cross-sectional flow formed when the barrier enters the spiral flow according to the present invention, respectively;

4 shows a linear flow of fluid generated by electromagnetic force propagation in a microchannel circular flow path,

5 is a view showing the helical flow of a fluid generated by electromagnetic force propagation in a microchannel circular flow path according to the present invention;

FIG. 6 is a view showing a micromixer which causes chaotic mixing by arranging one or a plurality of barriers in a microchannel inducing spiral flow through an electromagnetic force according to the present invention; FIG.

7a to 7f is a process flow chart sequentially showing the manufacturing process of the micro-channel lower plate generating the spiral flow in accordance with a preferred embodiment of the present invention,

8a to 8b is a process flow chart sequentially showing the manufacturing process of the micro-channel top plate causing chaotic mixing in accordance with a preferred embodiment of the present invention,

9 illustrates MHD BEM causing chaotic mixing according to a preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110, 120, 130: inside the Michael channel 111: electrodes arranged inside the micro channel

121, 141, 151: Micro channel wall 122, 132, 161: Barrier

123: Electrodes for electric field formation causing spiral flow

124: permanent magnet or electromagnet 131: elliptic point

133: hyperbolic point 140: microchannel causing linear flow

142, 152: electrodes installed on the outer side of the channel 143, 153: electrodes installed on the inner side of the channel

144: linear flow by electromagnetic force 150: microchannel causing spiral flow

154: anode installed on the channel bottom 155: cathode installed on the channel bottom

156: spiral flow by electromagnetic force 160, 183: micro mixer (MHD BEM)

162 and 182: microchannel top plate 170 and 180: substrate

171: metal such as Cr and Au 172: protective layer such as spin on glass (SOG)

173: photosensitive material such as SU-8 174: aluminum thin film electrode

175: electrode on the side wall of the channel 176: channel bottom electrode

177: microchannel lower plate 181: space for barrier formation

Hereinafter, a theoretical basis and a preferred embodiment of the micromixer presented in the present invention will be described with reference to the accompanying drawings.

1 is a view showing the flow of the fluid caused by the electromagnetic force propulsion. When the current (I) and the magnetic field (B) generated between the two electrodes 111 arranged in the channel 110 are arranged vertically, the electric field and the magnetic field are perpendicular to Fleming's left hand law (). Induces Lorentz force F in one direction, creating flow in the fluid inside the channel.

Figure 2 shows a cross section of the overall system structure according to the invention. On the side wall and bottom surface of the channel interior 120 generated by the channel walls 121, electrodes 123 are formed, which form an electric field which can cause helical flow, and the magnetic field is above or below the channel (or below). Up and down), a permanent magnet or an electromagnet 124 is disposed. It is also possible to induce chaotic mixing by means of one or more barriers 122 arranged on the channel wall based on the helical flow inside the channel created by a combination of suitable electric and magnetic fields. At this time, if the magnetic field is induced by a permanent magnet, it can be used to induce the Lorentz force by using a DC voltage. However, the use of a DC voltage can cause electrolysis at the electrode, so that an AC voltage can be used to induce a magnetic field by an electromagnet. When using an alternating voltage in this way, it is possible to induce a Lorentz force in a desired direction by applying an appropriate phase difference to the alternating voltage applied to the electrode. For example, when using an alternating voltage of a sine wave, by obtaining a Lorentz force as shown in Equation 1, it is possible to induce a Lorentz force in a direction that can be obtained by using a permanent magnet and a DC voltage. In addition, by applying an alternating current voltage having an appropriate phase difference with the voltage applied to the electromagnet to each of the electrodes, it is possible to simultaneously implement various flow patterns in the flow cross section with the pump effect by the electromagnetic force.

(Phi ~ is the phase difference between the voltage applied to the electromagnet and the voltage applied to the electrode.)

3A and 3B are diagrams respectively illustrating the cross-sectional flow form of the helical flow and the cross-sectional flow formed when the barrier enters the helical flow according to the present invention. As shown in FIG. 3A, an elliptic point 131 is formed in the sectional flow in the helical flow in the microchannel 130. In this case, the mixing performance is improved compared to the laminar flow, but the island structure is formed in the flow. Forming cannot bring great improvement in mixing performance. However, in the case of the cross-sectional flow of FIG. 3B, the barrier 132 has one hyperbolic point 133 and two elliptical points 131. In this case, a large stretching effect of the flow is obtained at the hyperbolic point. Can be. At this time, when the flow of FIG. 3A and FIG. 3B occurs periodically, chaotic mixing can be obtained by causing periodic disturbances in the helical flow inside the microchannel, thereby generating effective stretching and folding.

4 is a diagram showing a linear flow of fluid generated by electromagnetic force propagation in a microchannel circular flow path. The microchannel 140 causing linear flow has an anode applied to the electrode 142 provided on the outer side of the channel wall 141 and a cathode applied to the electrode 143 provided on the inner side when the magnetic field is acting upward. When applied, Lorentz forces can be generated in the flow direction shown in the figure to cause linear flow 144. In addition, as described above, when the AC voltage is used, the direction of the magnetic field is changed up and down, but the direction of the electric field generated by the electrode is also changed in this way, causing the Lorentz force in the same direction, thereby providing the desired flow. It is possible to produce.

5 is a view showing the helical flow of a fluid generated by electromagnetic force propagation in a microchannel circular flow path according to the present invention. As in the case of FIG. 4, the microchannel 150 that causes the helical flow has an anode applied to the electrode 152 provided on the outer side of the channel wall 151 and provided on the inner side when the magnetic field is acting upward. A cathode is applied to 153 to obtain a linear flow along the channel flow path. At the same time, the Lorentz force caused by the pair of anodes 154 and cathodes 155 provided on the channel bottom causes radial forces, and as a result, the Lorentz forces induced by the side and bottom electrodes are microscopic. This results in a helical flow 156 in the channel flow path. In addition, like the microchannel 140 that causes the linear flow, the microchannel 150 that causes the helical flow may also use the alternating voltage to cause the desired flow.

FIG. 6 is a view showing a micromixer in which chaotic mixing is caused by arranging one or a plurality of barriers in a microchannel inducing helical flow through an electromagnetic force according to the present invention. When one or a plurality of barriers 161 are arranged on the channel top plate 162 corresponding to the opposite side of the channel bottom surface in which the electrodes are installed in the microchannel 150 causing the helical flow by the electromagnetic force described in FIG. 5, It is possible to obtain chaotic mixing inside the microchannel based on the principle described in FIG. 3. The chaos mixer based on the basic concept described above will be named Magnetohydrodynamic Barrier Embedded Micromixer (MHD BEM, 160).

Now, a preferred embodiment will be described in detail with reference to FIGS. 7 and 9. In the following description of the present invention, when it is determined that detailed descriptions of related well-known technologies or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

7A to 7F are process flowcharts sequentially illustrating a lower plate manufacturing process of an MHD BEM according to an exemplary embodiment of the present invention. First, the substrate 170 such as glass is washed through a surface cleaning process, and then a metal 171 such as Cr / Au, which is to be an electrode, is deposited on the surface of the substrate through thermal deposition as shown in FIG. 7A to induce transverse flow. The designed electrode is formed through a general ultraviolet photographic process. As shown in FIG. 7B, the electrode is protected by using a protective layer 172 such as spin on glass (SOG) such that the electrodes fabricated in FIG. 7A are not affected by subsequent processes. As shown in FIG. 7C, the channel wall surface of the microchannel 177 that causes the helical flow is formed by using a photosensitive material 173 such as SU-8 using a general ultraviolet photographing process. As shown in FIG. 7D, an aluminum thin film or the like 174 to be an electrode on the side wall of the channel is formed using a process such as sputtering. The formed aluminum thin film 174 is formed as an electrode 175 on the side wall of the channel that causes the longitudinal flow by using a general ultraviolet photographing process as shown in FIG. 7E. Finally, by forming a channel bottom electrode 176 that induces transverse flow by etching the protective layer 172 such as SOG applied for electrode protection, a microchannel lower plate 177 that induces a spiral flow using an electromagnetic force may be manufactured. If the upper plate is covered on the lower plate, it is possible to fabricate a microchannel inducing a spiral flow by electromagnetic force propulsion.

8A to 8B are process flowcharts sequentially illustrating a top plate manufacturing process of an MHD BEM according to an exemplary embodiment of the present invention. After cleaning the surface of the substrate 180 as shown in FIG. 8A, a photosensitive material such as SU-8 is coated, and then a space 181 in which the barrier is to be formed is manufactured by a general ultraviolet photographing process. This process yields a master (or mold) with a frame from which the top of the MHD BEM can be fabricated. Now, if the master of FIG. 8A is molded by using PDMS (Polydimethylsiloxane) or the like and cured, the top plate 182 of the MHD BEM including the barrier 161 as shown in FIG. 8B may be obtained.

9 is a view showing a state in which the manufacturing of the MHD BEM according to an embodiment of the present invention is completed. The lower plate 177 and the upper plate 182 of the microchannels manufactured by FIGS. 7 and 8 may be plasma-bonded to prepare an electromagnetic force-propelled chaotic micromixer (MHD BEM) 183 including a barrier.

As described above, according to the present invention, it is possible to induce chaotic mixing inside the microchannel by arranging one or a plurality of barriers inside the microchannel causing the helical flow by the electromagnetic force, so that the mixing performance is greatly reduced. The mixing performance can be raised significantly. In addition, the barrier is simple in shape, and has the advantage of greatly reducing the pressure loss with respect to the driving of the flow driven by the electromagnetic force.

In particular, the MHD BEM presented in the present invention can be easily introduced into the microchannel together with an analysis structure that performs other functions in the entire analysis system such as a micro-total analysis system (Micro-Total-Analysis-System) to manufacture micro devices such as biochips. It will be easy to introduce into the process.

On the other hand, the present invention can be variously modified by those skilled in the art within the spirit and scope of the present invention based on the basic concepts and embodiments described above.

Claims (8)

On the side walls and the bottom surface of the microchannel are arranged electrodes which form an electric field which can cause a helical flow, Magnetic field generating means for forming a magnetic field around the outside of the micro-channel is installed, And one or a plurality of barriers arranged on the microchannel wall to induce chaotic mixing. The method of claim 1, A permanent magnet is used as the magnetic field generating means, and the electromagnetic force-propelled micromixer with a barrier, characterized in that to induce a current by a direct current voltage. The method of claim 1, Electromagnet is used as the magnetic field generating means, the electromagnetic force-propelled micromixer with a barrier, characterized in that to induce a magnetic field and current with an alternating voltage. The method of claim 1, And the magnetic field generating means is located above or below the microchannel, or above and below the microchannel. The method of claim 1, And the barrier is formed above or below a wall of the microchannel wall. Depositing a metal on the surface of the first substrate by thermal evaporation, and then forming an electrode through an ultraviolet photography process; Forming a protective layer on a surface of the substrate on which the electrode is formed; Forming a microchannel wall surface inducing a spiral flow on the protective layer through an ultraviolet photographic process; Forming an aluminum thin film on the microchannel through a sputtering process; Forming an electrode on the side wall of the channel to induce longitudinal flow of the aluminum thin film through an ultraviolet photographing process; Etching the exposed protective layer inside the channel to expose a channel bottom electrode causing a cross flow to fabricate a microchannel underplate; Applying a photosensitive material on the second substrate and forming a space where a barrier is to be formed through an ultraviolet photographing process or the like; Manufacturing a microchannel upper plate by molding and curing the polydimethylsiloxane (PDMS) on the second substrate; Electromagnetically-propelled chaos micromixer manufacturing method comprising a barrier comprising the step of adhering the top and bottom of the micro channel. The method of claim 6, The electrode is a micro mixer manufacturing method provided with a barrier, characterized in that the Cr / Au metal. The method of claim 6, The protective layer is a micro mixer manufacturing method provided with a barrier, characterized in that the SOG (Spin On Glass).